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LT1-LT4 Modifications
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Old 11-30-2004, 01:46 AM   #1
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Default LT1 Heads : Iron Vs Aluminum

The iron head is supposed to flow better than the aluminum one, but the aluminum one would be much better for more timing and heat.

Once ported, will both heads flow close the same, or can the iron head make bigger power numbers?
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Old 11-30-2004, 02:15 AM   #2
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where do you get the iron flows more?
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Old 11-30-2004, 05:57 AM   #3
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The iron heads do flow more than the aluminum heads. Roughly 220 CFM @ 0.5 inches lift, 28 inches water column for the aluminum heads and 230 CFM @ 0.5 lift and 28 inches water column for the iron heads. The only problem is that aluminum has a higher specific heat than iron and thusly allows you to run a higher CR without risk of detonation.
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Old 11-30-2004, 07:42 AM   #4
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well every set we have flowed came up with a 1-3 cfm diffrence in no order at all.
they will make the same power with both being ported by the same guy but the irom you gain weight and loose max compression without detonation. but who runs stock heads anyway?
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Old 11-30-2004, 10:28 AM   #5
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Quote:
Originally Posted by METALBEAST
The iron heads do flow more than the aluminum heads. Roughly 220 CFM @ 0.5 inches lift, 28 inches water column for the aluminum heads and 230 CFM @ 0.5 lift and 28 inches water column for the iron heads. The only problem is that aluminum has a higher specific heat than iron and thusly allows you to run a higher CR without risk of detonation.
Well kind of.... the aluminum disapate the heat more and do not get as hot, also the weight less, but I seriously doubt that Alloy heads withh hold more compression than Iron heads.
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Old 11-30-2004, 11:51 AM   #6
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Quote:
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Well kind of.... the aluminum disapate the heat more and do not get as hot, also the weight less, but I seriously doubt that Alloy heads withh hold more compression than Iron heads.
Fact is the aluminum heads expand more with heat allowing compression drop.
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Old 11-30-2004, 12:44 PM   #7
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Quote:
Originally Posted by Squat13
Well kind of.... the aluminum disapate the heat more and do not get as hot, also the weight less, but I seriously doubt that Alloy heads withh hold more compression than Iron heads.

Not kind of, its cold hard fact. Specific heat is defined as the ratio of the change in internal energy of a substance to the amount of incremental change in temperature per unit volume. The specific heat of iron is numerically higher than that of aluminum. Therefore it takes a greater amount of temperature change to raise the internal energy of aluminum than it does iron (aluminum does not absorb as much heat as iron) and thus not be as susceptible to detonation (spark knock, preignition) as iron.

The temperature of a fluid will increase with a corresponding increase in pressure ( this is accomplished when by increasing your CR for example). Therefore aluminum heads can run higher compression ratios than equivalent iron heads.
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Old 11-30-2004, 02:45 PM   #8
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Thanks for the replies guys. I have the oportunity to pick up a rebuilt Iron head LT1 with 0 kms for $800 cnd and was wondering if it was worth it. I am looking to get a rebuildable block and aluminum heads for my winter project and thought this may be a good choice. Looks like I will have to keep searching.

Thanks.
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Old 11-30-2004, 03:57 PM   #9
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Quote:
Originally Posted by Boother
Thanks for the replies guys. I have the oportunity to pick up a rebuilt Iron head LT1 with 0 kms for $800 cnd and was wondering if it was worth it. I am looking to get a rebuildable block and aluminum heads for my winter project and thought this may be a good choice. Looks like I will have to keep searching.

Thanks.
EBAY OR EVEN HEAD PORTERS HAVE PLENTY OF LT1 STUFF AROUND. $800 SHOULD BUY A GOOD BIT.
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Old 11-30-2004, 09:03 PM   #10
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Iron heads outflow the 95 and earlier aluminums the 96-7 aluminums are roughly equal in flow to the irons. If you want to get into thermodynamics aluminum transfers heat faster sucking more heat out of the chamber, now think for a moment what does an engine do turns heat into rotation right so every bit of heat not used to turn the crank is wasted. aluminum does allow more compression due to the lesser themal effiency, the extra compression is then used to make up for the power lost though cooling. The weight difference is only about 35# as per a source I trust a whole lot more than the average forum poster.

The irons can be ported to flow well if going all out on the porting though I think the best are the early aluminum heads because there is more material to play with.
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Old 11-30-2004, 09:36 PM   #11
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Quote:
Originally Posted by FIREHAWK#608
EBAY OR EVEN HEAD PORTERS HAVE PLENTY OF LT1 STUFF AROUND. $800 SHOULD BUY A GOOD BIT.
Just to clarify, I could get the entire, brand-new rebuilt engine for $800 cnd, which would be about $500 US, and it is local.

Right now, Ebay cannot touch that deal.
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Old 12-01-2004, 06:50 PM   #12
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For that take it even if you sell the heads, heck worth it even if you throw the heads away, but like several of us have said they are a good head just not as light as aluminum
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Old 12-01-2004, 06:57 PM   #13
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aluminum will be lighter on the car and still give u alot of hp edelbrock makes a kit for the lt1s
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Old 12-01-2004, 07:41 PM   #14
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get that engine if its rebuilt and good.
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Old 12-02-2004, 01:42 AM   #15
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Quote:
Originally Posted by 96capricemgr
Iron heads outflow the 95 and earlier aluminums the 96-7 aluminums are roughly equal in flow to the irons. If you want to get into thermodynamics aluminum transfers heat faster sucking more heat out of the chamber, now think for a moment what does an engine do turns heat into rotation right so every bit of heat not used to turn the crank is wasted. aluminum does allow more compression due to the lesser themal effiency, the extra compression is then used to make up for the power lost though cooling. The weight difference is only about 35# as per a source I trust a whole lot more than the average forum poster.

The irons can be ported to flow well if going all out on the porting though I think the best are the early aluminum heads because there is more material to play with.
Execellent point At the same compression ratio, an iron head will be more efficient than an aluminum head. However, the thermal efficiency of an IDEAL spark ignition IC engine is defined as

TE = 1- (CR)^(1-K) where

TE = Thermal efficiency

CR = Compression Ratio

K = specific heat ratio of the working fluid ( in our cas the air/fuel mixture which would be identical regardless of head material)

I underdstand that real IC engine are not ideal since we must also take into account friction, head design etc. But it hold true to an extent. Therefore the engine with a higher CR will be the most efficient engine. Just my $0.02
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Old 12-02-2004, 01:42 AM
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